Jetty or breakwater.



iatented Nov. 2e, |901.

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(No Model) Fif.

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UNITED STATES PATENT OFFICE.

LEWIS M. HAUPT, OF PHILADELPHIA, PENNSYLVANIA.

JETTY oR BREAKWATER.

SPECIFICATON forming part of Letters Patent No. 687,307, dated. November26, 1901.

Appnmitn inea April a, 1901.

To a/ZZ whom it may concern:`

Be it known that I, LEWIS M. HAUPT, a resident of Philadelphia,Pennsylvania, have invented a new and useful Improvement in. Jetties orBreakwaters, which invention is fully set forth in the followingspecication.

This invention is an improvement upon that secured to me ink LettersPatent of the United States bearing date April 3, 1888, and numbered380,569, for a dike or breakwater, and combines the general laws andprinciples stated therein, with the additional factors evolvedv fromfurther research into and experience with the actual movements ofcurrents in the open sea, as well as under the restraining influences ofcurved directrices, augmented by the force of gravity, operating on adescending instead of afn ascending gradient, also by reversing theusual order of constructing said directrices by beginning to create thereaction and performing-the work first on the outer or downstream faceof a bar instead of the inner or land slope. The extensive Works whichhave been constructed in this department of applied science during thepast score of years have served to demonstrate the great expense andimpractieability of securing self-maintaining channels by the use ofparallel or convergent jetties in pairs, Whether straight or curved,whatever may be their height, and it has been found necessary to haverecourse to dredging to create and maintain channels of sufficientdimensions to meet the present demands of commerce. These dredges are inthemselves expensive to build and maintain, and the channels created bythem on straight lines being artificial l are constantly tending toshift to the natural curves demanded by the local conditions of thesite. Thus increasingly larger lsums are required annually for thecreation and maintenance of channels by mechanical devices inconsequence of the demands due to the greater draft of vessels, whilethe same or even more capacious natural channels might be secured by theapplication of the combined static and dynamic forces of gravity,momentum, impact, reaction, and other hydromechanical agencies inherentto flowing water.

Before describing the improvement in detail it is important to note thatthe alluvial at tidal estuaries or inlets.

Serial No. 54,625. (No model.)

bars obstructing ocean commerce are of two classes-evin., one known asthe drift and wave bar, ,caused by the deposit in front of vthe entranceof beach sand or littoral drift 2 carried by Waves, tides, and currentsalongshore, the other known as delta bars, formed from `the sedimentbrought downby the land-drainage and deposited in front of the mouth ofsilt-bearing streams. Thefirst class is dependent for its depth over thebar upon tidal movements and is therefore found The second depends uponthe fluvial waters and is located at the mouth of rivers. The source ofthe material forming the bars in these cases being different thetreatment must vary accordingly. l

The devices embraced in my former patent were chiefly applicable totidal inlets and were especially designed to arrest and control thelittoral drift, to utilize the tidal energy by opposing as littleresistance as practicable to the free ingress of the tides to theinterior bays, that the volume of the movement at ebb might not beimpaired; also, that the proposed channel might be defended from theencroachment of the sand drifting along the coast and that the ebbdischarge might be confined to a limited sector of the bar, and thus itseffective Work (as compared with that of the flood) be made the greater,or, in other words, the conditions of equilibrium of the flood and ebbshould be changed in favor of the ebb forces.

In this improvement the purpose is more particularly to apply the energyof the fluvial waters, charged with their own sediment, in such' manneras to create, erosion, produced by the concentration and reaction of apermanent opposing medium placed in or near their path and resulting inthe deposition of sediment upon the opposite flank vof the channel fromthat upon which the artificial structure is erected. There is thereforea radical distinction in the devices applicable to these two classes ofmaritime works and in the method of applying these jetties ortools, asWell as in their form and location. In'the first case (see Patent No.380,569) the structure is detached from the shore-line and is composedof intersecting curves, forming cusps and having rectilinear flanks. Inthe IOO lli

second itis attached to the proper bank of the river (whichever that maybe) of which it forms an extension and is composed of a series ofcontinuous curves connected tangentially to secure an accumulation ofenergy and a continuous reaction along or parallel to the axis of theproposed channel. The curvature may be increased toward the outer end ofthe work to compensate for the loss due to impact and friction. Theseobjects will be more clearly set forth by the following enunciation ofthe laws and principles which it is intended to utilize in thisinvention for securing new, useful, and economic results.

First. Depth in bends.-The well-known fact that the greatest depth ofWater in a stream is as a rule located on the concave -bank of a bend,while in the straight reaches the channel has less depth and is ofuncert-ain position.

Second. Depth a function offrcd'iusf-lhat the depth in the bends for agiven stage is a function of the radius of curvature and variesinversely as said radius, other things being equal. It is furtherobserved that as the curves of the bed are stronger the more remarkableis the depth produced by a great pressure of water caused by aconvergence of the water-threads toward the concave bank.

Third. Head duc to centrifugal force.-A That this depth is not dueprimarily to the surface slope of a stream which in a bend is longer onthe concave bank, but to the head of water created by 1 he centrifugalmotion of the Huid, causing downward, as well as longitudinal,movements, thus producing a helicoidal resultant or boring action on thebot- 1rom. Observation on currents show that deepening increases notwith the velocity of the current, but rather with the head of waterworking on the deepening, and especially at au increased depth.

` Fourth. T/Vorh duc to mpuct-The rate of erosion of alluvial banks orbeds is also largely due to the differences of the velocity of thefilaments of an impinging stream before and after impact, and thisdifference is a function of the radius of the curve. Hence the sharperthe curve the greaterits erosive effects and the deeper the channel. Inthe expression :5B-L (V2-V12) the greatest amount of work will H resultfrom the greatest difference of veloci` ties between V and V1 before andafter impact. If V1 is zero, the maximum result will be secured; but itmay be excessive, injurious, or'

discontinuous. Hence the necessity for a careful adjustment to localrequirements by If they are equal, the work will be nil.

Fifth. Ovcrcontracton or ovcrcptmsz'on.- In sedimentary rivers the banksat the outlet are natural levees constructed by the action of thestream, and any artificial aids in the shape of two jetties or leveesprojected seaward which are either too close together or too far apartbecome injurious in restricting the discharge and in creating bars inthc channels above the mouth of the stream.

Sixth. Concentration.Every silt-bearing river is merely a hydraulicconveyer, having the inherent energy to build bars or carve outchannels, and a careful study of the natural agencies and conditions atWork will suftice in many instances to ameliorate the crossing-bars andconvert them into navigable channels. Mere narrowing is not sufficient.The threads must be made to takea convergent direction, thus increasingM and V and diminishing V1. This may be best secured by a single concavestructure, located to produce concentration and reaction simultan@ously.

Seventh. Lateral transportation. The mouths of such rivers areobstructed by their own sediment, which is deposited by the inertia ofthebody of water into ulrich they debouch. The source of the materialforming these delta-bars being coincident with the stream itself, theinterposition of a barrier simply to arrest this drift cannot be applied without damming up the channel. The action of the currents must bechanged by a properly-located artificial curved jetty, so as to causereaction on the bed, accompanied by a lateral transposition and depositof the silt in quiet waters and out of the path of coinmerce. Thus therewill be constructed automatically and Without extra cost a natural bank,which must of necessity adjust itself to the regimen of the stream,since it is built by it, and which will meet its requirements far betterthan can be done by any auxiliary Work of man.

Grafvityf-It is also observed that the erosive action of a currentpassing over a bar is more effective on its downstream slope, where itis aided by the force of gravity, than on the Hatter upstream face,where the material must be carried out over it on an ascending grade andis continually accumulating to obstruct its own path. Hence the trueorder 0f `procedure in works of amelioration should be so to constructthem as to begin the application of the energy of the currents by theirconcentration and reaction on the outer or downward face of theobstructing shoal and to increase their intensities by the landward (asdistinguished from the usualseaward) extension of the Works as theerosion proceeds.

Applications-By applying these means and order of procedure the outercontours are caused to recede instead of to advance. The material isrolled downhill instead of up and is not obstructed by aconstantly-augmenting deposit, which is ordinarily piled and pushedoutward as the work advances.

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The method of building out from the shore has invariably had the effectof pushing the crest of the bar rapidly to sea without materiallyincreasing its depth by natural scour. In some places this advanceduring construction has amounted to more than half a mile a year andhasaggregated three'miles in the process of the work, thus adding over sixlniles to the length of the twin jetties in deep Water and involving theuseless expenditure of many millions of dollars. It is one ofthe objectsof this improvement to avoid this difficulty.

The reversal of the usual method of procedure by starting work from afloating plant on the outer or sea slopeinstead of from a scaffolding ortramway built out from the shore will therefore result in far greatereconomies and expedition in the formation of the channel and will alsoavoid to a great extent the erosion from cross-currents at the head ofevery protruded jetty, which increases the cost,as well as theaccumulation of energy, which renders the construction more difcultand'dangerous. Under the present system of straight or parallel twinjetties the riverV sediment must traverse the entire length of the workbefore it cau escape into deep water. As this length increases with thatof the jetty the water-slope is reduced, and consequently its carryingcapacity is diminished, while there is no room for deposit until thedeep water is reached in front of the works. The result has been eitherto congest the outfiow by overcontraction between jetties too closetogether, thus dam'ming up the river above and causing a rapidsilting-up of its bed, as at the South Pass of the Mississippi, or thecarrying of the sediment to sea and depositing it in front of theentrance, where a new bar is soon formed.

I am aware that single jetties have been built at the mouths ofsilt-bearing rivers; but they have been projected from the shore sea-Ward in every instance, so far as records are available, or they havebeen curved away from the channel, thus presenting a convex instead of aconcave front, or they are built submerged or else only to low water ormidtide, and thus have failed to utilize the full tidal volume, as Wellas the hood-discharges, of the land-drainage, and for these and otherreasons have failed to combine and utilize all the available forces ofnature to produce the most economical and greatest results as to depth,capacity, and self maintainance of channels.

In View of the variable physical conditions existing at every site eachcase becomes a special problem of itself, so that no one specific formcan be generally applied. Hence I do not wish to be limitedin the use ofmy invention to any particular degrees of curvature nor order of theirarrangement, but desire to apply the general principles and forcesalready enumerated tothe order of construction above specied (buildingfrom bar inward) in such manner as to produce conti-` nuity of reactionacross the bar, yrecession of outer contours, prevention of bar advance,avoidance of deep pockets at endsof work,

economy in ccnstruction,and enlarged channel dimensions consequent uponthis method of applying the availableforces. J

It is designed to make the jetty the tool throughY which the potentialenergy of the natural forces is applied to secure and maintaincommercial channels, and the results are inseparably connected not onlywith the form of the tool, but with the manner of its application. Underthese circumstances a drawing would seem to be unnecessary; but to aid amass (M) of water with a mean discharge of about two hundred thousandcubic feet per second and a mean .velocity (V) of about 2.8 feetmaintains a 'depth by impact of from seventy to one hundred feetbetweenl banks which are a quarter of a mile apart and where the radiusof the bend is three miles, while a radius of 4.43 miles with the samemass maintains a mean depth of channel of sixty-six feet, having a meanwidth between thethirty- IOO five-foot contours of over one thousandfeet.

On the crest of the bar four miles from land, the current beingunsupported, the depths are reduced, however, by inertia of the Gulfwaters tofrom ten to twelve feet for adistance of one mile.

I n the accompanying drawings, which form part of this specification, Ihave for the purposes of illustration represented one application of myinvention.

Figure l is a plan view; Fig. 2, a cross-section on line H L, and Fig. 3a longitudinal sectionon the axis of the channel.

The application of the laws of hydromechanics to this special case wouldbe best ful- -tilled by a single curved jetty A B C D, Fig. l,

starting from the outer slope of the bar at A and having in this caseradii varying from three to Iive miles, curving toward the lands endknown as East Point on the left or eastern bank of .the pass for adistance of about two miles, and thence by a curve of an infinite radiusreaching the fast land and closing the jetty completely at D. The formof jetty adapted to this location is shown in Fig. l, where thetopography is represented in five-foot contours. The proposed jetty eX-tends from the sea-slope at A to the shore on the left or east bank atD. The channel is represented approximately in its natural condition. Itis defended from the waves of the trade-winds by the projecting jetty,acting l'IO also as a breakwater and an aid to navigation.

The flexure to the westward serves to maintain an open entrance byfacilitating the passage of the littoral current and the removal by itof any sediment that may reach the outer end of the jetty in course oftime. The crest of the bar is ovoidal, as shown by the curve, Fig. l.There is a littoral current moving westwardly; but the main source ofthe detritus is the river, which, it is estimated, carries one hundredand two million cubic yards of sediment to the Gulf annually and causesthe bar to advance at the rate of one mile in twenty years. By this formof single jetty this rate will be considerably reduced and the materialbe diverted to the extensive mudflats to the west of the channel, asindicated. The centers of the various arcs are indicated at E, F, and G,while their radii vary from infinity to a minimum limit to be determinedby the volume and velocity of the stream.

The dotted arrows s s s indicate the general dispersion of the currentsin a state of nature. Those which would pass to the eastward areintercepted by the jetty and confined to the channel, thus increasingthe volume passing over this morelimited section of the bar. As thelevee to the west becomes built up by natural deposits the scour betweenit and the artificial jetty or bank becomes still moreeffectiveandthechanneldeepens. Thefigures 20, 25, 30, duc., indicate thedepth of water at various points. These results are indicated in Fig. 2,which is across-section on the line H L of Fig. l, which shows theoriginal bottom before improvement and the deepening from the action ofthe currents as controlled and regulated by thecurved jetty. To expeditethe formation of this channel, it may be desirable to dredge thematerial ont, in which case it should be impounded behind the jetty andout of reach of the currents, as indicated in the dump P.

Fig. 3 is a section of tho bar to illustrate thedifference in thedegrees of the inner and outer slopes and to show the utility ofcommencing the work on the outer face of the bar and working withinstead of against the force of gravity. A jetty begunat A A' would haveno resistance in front of it and would scour downhill, while ifcommenced at I) D it would be necessary to roll or carry the detachedsilt up and over the crest of the bar, which would form a lee to preventfurther transportation and invite deposit, thus advancing the barseaward as the work progresses. By this single curved jetty, thuslocated and constructed, I combine silnultaneously the available naturalforces of the stream to prod ucemore rapid erosion of the channel andalso 011e that is more readily maintained at less cost than by any knownmeans.

Having thus described and stated the general principles upon which myinvention is based, as well as their application to a special case, towhich, however, I do not limit myself, I therefore proceed to set forththe claims which I desire to secure by Letters Patent, as follows:

1. A single jetty or breakwater rising to or above the high-water orflood level, composed of a combination of non-intersecting curves ofvariable radii; the concave side of one or more of the curves facing thecurrent,substan tially as and for the purpose set forth.

2. A single jetty or breakwater composed of variable radii; the lengthof said radii depending on and being adjusted to the volume and velocityof the currents; said jetty being built on the Windward side of thechannel (as determined by the direction of the resultant, littoralforces) and having the concave side of one or more of its curves towardthe current substantially as and for the purpose set forth.

3. The method of constructinga single jetty or breakwater by beginningthe construction on the outer or down-grade slope of the bar anddeveloping it on curved lines toward the land; the curves, or at leastone of them, having its concave side toward the currents, substantiallyas and for the purpose set forth.

4. A single jetty or breakwater composed of a combination ofnon-intersecting curves connected tangentially and having their concavefaces toward the current and their con- Vex faces toward the resultantlittoral drift to create and maintain a continuous reaction across thebar in combination with the action of gravity secured by the method ofconstruction from the outer slope landward substantially as and for thepurpose set forth.

In testimony whereof I have signed this specification in the presence oftwo subscribing witnesses.

LEWIS M. HAUPT.

Witnesses:

BENI. FRANKLIN, BELLE C. HAUPT.

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